This invention relates to throttle body for an internal combustion engine, and more specifically, the invention relates to a throttle body suitable for integration with a plastic component of an air induction system.
A throttle body regulates the flow of air from the atmosphere to an intake manifold that provides an air/fuel mixture to engine combustion chambers. Providing maximum airflow to the combustion chamber enables the engine to reach maximum power. The engine produces a minimum amount of power when airflow is almost entirely restricted, such as when the engine is idling. Of course, airflow must be regulated by the throttle body between maximum and minimum engine power so that the engine may perform under a variety of vehicle operating conditions.
The throttle body includes a throttle blade that is secured to a throttle shaft which is pivotally supported in a throttle body. The throttle blade is situated in an air passageway that carries fresh air to the intake manifold. The throttle shaft is rotated by a cable, solenoid, or other actuator to rotate the throttle blade between a variety of positions to regulate the flow of air to the manifold. The throttle blade and air passageway must mate or seal to prevent leakage when the throttle is closed and provide consistent air flow at a given throttle blade position during various operating conditions. Typically, the throttle body is constructed from aluminum or magnesium and is secured to an aluminum or magnesium intake manifold by threaded fasteners. Recently, plastic throttle bodies have been used in air induction system designs to reduce the weight and cost of the engine. However, the automotive industry has not widely accepted plastic throttle bodies because of concerns that the throttle bodies are not robust enough. Specifically, a throttle body is subjected to heat fluctuations that may significantly impact the dimensional stability of the throttle body and permit warping. As a result, an unacceptable amount of leakage could occur between the throttle blade and air passageway. Therefore, what is needed is a lighter, less expensive throttle body that provides an adequate seal between the throttle blade and the air passageway. Specifically, a throttle body is subjected to heat fluctuations that may significantly impact the dimensional stability of the throttle body and permit warping. As a result, an unacceptable amount of leakage could occur between the throttle blade and air passageway. Therefore, what is needed is a lighter, less expensive throttle body that provides an adequate seal between the throttle blade and the air passageway.
The present invention provides a throttle body assembly for an internal combustion engine. The assembly includes an insert having an opening and opposing bores arranged transverse to the opening. The insert is constructed of a first material, preferably a metal such as aluminum or magnesium. A throttle shaft is supported by the bores and spans the opening. A throttle blade is disposed within the opening and secured to the shaft. Both the throttle blade and throttle shaft are preferably constructed from a metal so that the seal between the throttle blade and the insert remains dimensionally stable. A body defines an air passageway with the insert at least partially disposed within the body and aligned with the air passageway. The body is constructed from a second material different from the first material, such as a composite plastic. The body may be a portion of an intake manifold. Accordingly, the above invention provides a lighter, less expensive throttle body that provides an adequate seal between the throttle blade and the air passageway so that a metal throttle body is no longer required.